Hie am s



H. s. MAXIM."

I I ELECTRIC LAMP. No, 247,380. Patented Sept. 20,1881.

1 2% 1 Illtllllll amt? W 'r rr eases. n w lFP/EE'LEIK UNITED STATES PATENT OFFICE.

HIRAM S. MAXIM, OF BROOKLYN, NEW YORK.

ELECTRIC LAMP.

SPECIFICATION formingpart of Letters Patent No. 247,380, dated September 20, 1881. Application filed December 22, 1879.

To all whom it may concern:

Be it known that I, HIRAM S. MAXIM,of the city of Brooklyn, county of Kings, and State of New York, have invented certain new and useful Improvements in Electric Lamps, of which the following is a specification, reference being had to the accompanying drawings, which are designed to form a part hereof.

My invention relates especially to the class of lamps known as incandescent lamps, in which a single continuous electrode is used, and in which the light is produced by heating the electrode to incandescence by passing through it a current ofelectricity. In such lamps, as they have heretofore been constructed, the electrode has been constantly liable .to destruction by fusion, as its temperature has to be raised nearly to the fusing-point of the material of which it is constructed and maintained thereduring all the time that the lamp is in use. Under such circumstances a slight increase in the current above its normal 1strength fuses the electrode and destroys the amp.

My improvement consists of an automatic device operated by the heat of the lamp, whereby the incandescent strip or electrode is relieved by shunting off a part of the current through another circuit whenever the electrode becomes dangerously heated.

In the drawings, Figure l is an oblique view of a lamp constructed in accordance with my invention, and Fig. 2 is a vertical section of the same, taken at a line slightly removed from the center.

A is a base, made of wood or other non-conducting material.

B is a metallic bed-plate, having affixed to it an overhanging arm, 0.

D is a flat horizontal spring attached at one end to the bed-plate B, and insulated from it byablock of insulating material. It has a binding-post, E, to receive one wire of the circuit.

F is a rod or spindle passing through a vertical hole in the arm-O at its extremity, and having a screw-thread out upon it, carrying the adjusting-nut I.

G is a small set-screw inserted in the arm 0,

and working in a groove in the side of the rod F, to keep it from turning.

H is a ribbon-shaped electrode or strip of conducting material, preferably platinum, held in clamps attached to the lower end of the rod F and the outer end of the spring D.

K is a metallic pin or post erected under the lower clamp of the electrode, insulated from the bed-plate B, and extending down into the base A.

L is a binding-post to receive the other wire of the circuit. It is electrically connected with the arm 0 and the post K.

The operation of this device is as follows: The spindle F is so adjusted by means of the nut I that the lower clamp of the electrode just clears the post K when the electrode is heated to the desired degree of incandescence. The current then passes from the binding-post E through the spring D, the electrode H, the spindle F, and the arm 0, and its connection to the binding-post L, and thence back to the source of electricity. If, however, the current increases in strength, however slightly, the electrode becomes more highly heated andincreases in length, allowing its lower clamp to drop down into contact with the post K when the current or apartofit is shunted off through K and its connections to the binding-post L. As soon as the temperature of the electrode becomes sufficiently reduced it contracts and opens the shunt, thus causing the full current to pass through the electrode again.

It will be observed that this device is entirely automatic and certain in its operation. It is very sensitive and susceptible of delicate adjustment.

A globe of the usual form may be used with this form of lamp, and the shunt may be operated by a strip or rod of metal other than the light-giving portion of the lamp placed in the circuit for that purpose-as, for example, by the rod E, which may be made of any suitable size and material.

A lever, either with or without a spring, may also be used in place of the spring D, and the insulation of the post K from the bed-plate is not essential unless it is desired to interpose a resistance-coil between K and L, in which case such coil may be placed in the hollow thermostaticcircuit-regulator,substantially as base A. described, and for the purposes set forth.

My invention relates, broadly, to an auto- 2. In combination with an electric light, a matic shunt or circuit-regulator operated by thermostatically-operated shunt, substantially 5 the heat of the lamp. 5 as described, and for the purposes set forth.

Having descrihedrny invention, whatI claim as new, and desire to secure by Letters Pat- HIRAM MAXIM ent, is- Witnesses:

1. In combination with an electric-light hav- CHAS. G. GLAGGETT, 1o iug a continuous incandescent conductor, a, LEONARD E. CURTIS. 

